This invention relates to the use of compounds belonging to the group of vitamin B6 and derivatives thereof for improving the structure and strength of hair keratin and the fastness to washing of hair colors in preparations for topical application.
Hair keratin is structurally damaged by regular treatment with alkaline, strongly reducing or oxidizing chemicals, for example in permanent waving, coloring or bleaching of the hair. Such damage is reflected in a weight loss, in a reduction in the melting point of the keratin and in increasing fragility, poor combability and a deterioration in the hold and body of the hair. In addition, structurally damaged hair is often dull and lackluster in appearance.
To overcome this drawback, structure-improving additives, for example formaldehyde and formaldehyde donors, S-acetyl succinanhydride, ammonium vinyl phosphonate, ammonium phosphate, boric acid, oxazolidines, reducing sugars, tocopherols or so-called onic acids (for example gluconic acid), have already been added to hair-care preparations. Although such additives are effective to a certain extent, their effect on seriously damaged hair is still unsatisfactory. Accordingly, there was still a need to find structure-improving additives for hair which would be suitable for treating the hair after permanent waving or coloring processes.
Pyridoxine (pyridoxol) and other compounds belonging to the vitamin B6 group have already been proposed for use in hair tonics for reducing refatting and for stimulating hair growth.
EP 0678293 A2 proposes topical compositions containing pyridoxine tripropionate for treating the hair and skin. EP 001079 A1 describes describes anti-seborrheic cosmetic compositions containing pyridoxine tripalmitate as their active ingredient.
The present invention relates to the use of vitamin B6 derivatives corresponding to formula (I): 
in which
A and B independently of one another represent hydrogen, halogen, a C1-4 alkyl group, a C3-6 cycloalkyl group, a C1-4 monohydroxyalkyl group, a C2-4 oligohydroxyalkyl group, a C1-4 aminoalkyl group, a group xe2x80x94OR or a group xe2x80x94NR1R2, where R1 and R2 independently of one another represent hydrogen, a C1-4 alkyl group or a C1-4 monohydroxyalkyl group or R1 and R2 together with the nitrogen atom form a saturated ring,
C represents a group xe2x80x94OR, xe2x80x94NR1R2, xe2x80x94OP(O)(OR3)2, a C1-4 monohydroxyalkyl group, a C2-4 oligohydroxyalkyl group or a C1-4 alkyl group,
D represents a group xe2x80x94OR, a carboxy group, a C1-22 alkoxycarbonyl group, a formyl group, a group xe2x80x94CH2OR or a group xe2x80x94CH2xe2x80x94NR2,
E represents a group xe2x80x94OR, xe2x80x94OP(O)(OR3)2, a C1-4 monohydroxyalkyl group or a C2-4 oligohydroxyalkyl group,
R representing hydrogen, a C1-4 alkyl group, a C1-22 acyl group, a hydroxy-C2-22-acyl group, a C2-10 carboxyacyl group, a C3-10 oligocarboxyacyl group, an oligocarboxymonohydroxy-C3-10-acyl group, an oligocarboxyoligohydroxy-C3-10-acyl group, a C3-8 cycloalkyl group, a C1-4 monohydroxyalkyl group, a C2-4 oligohydroxyalkyl group, an aryl group which may contain a hydroxy, nitro or amino group, a heteroaromatic group or a group xe2x80x94CH2CH2NR1R2, where R1 and R2 are as defined above,
R3 representing hydrogen or a C1-5 alkyl group,
or one of the corresponding physiologically compatible salts, for improving the structure and strength of hair keratin and the fastness to washing of hair colors by topical application of preparations containing these derivatives/salts.
Compounds corresponding to formula (I) in which one of the two groups A and B is hydrogen are preferred.
Compounds corresponding to formula (I) in which one of the two groups A and B is hydrogen and the other group is a C1-4 alkyl group are preferred.
Other preferred compounds of formula (I) are those in which C is a hydroxy group, a C1-4 monohydroxyalkyl group or a C2-4 oligohydroxyalkyl group.
According to the invention, compounds of formula (I) in which D is a hydroxymethyl group, a hydroxy group, a carboxy group, a group xe2x80x94CH2xe2x80x94NR2 or a formyl group are preferred.
Other preferred compounds of formula (I) are those in which E is a hydroxy group or a group xe2x80x94OP(O)(OH)2.
Particularly preferred compounds corresponding to formula I are pyridoxine (A=H, B=CH3, C=OH, D=CH2OH, E=OH), pyridoxal (A=H, B=CH3, C=OH, D=CHO, E=OH), pyridoxal-5xe2x80x2-phosphate (A=H, B=CH3, C=OH, D=CHO, E=OP(O)(OH)2) and pyridoxamine (A=H, B=CH3, C=OH, D=CH2NH2, E=OH).
Examples of C1-4 alkyl groups in the compounds according to the invention are methyl, ethyl, n-propyl, isopropyl, n-butyl and tert butyl. Preferred alkyl groups are methyl and ethyl. Methyl is a particularly preferred alkyl group. Preferred C3-6 cycloalkyl groups are cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl. Cyclohexyl and cyclopentyl are particularly preferred groups. Preferred C1-4 monohydroxyalkyl groups are the groups hydroxymethyl, 2-hydroxyethyl, 3-hydroxypropyl or 4-hydroxybutyl; hydroxymethyl and 2-hydroxyethyl are particularly preferred monohydroxyalkyl groups. A preferred C24 oligohydroxyalkyl group is the 1,2-dihydroxyethyl group. Preferred C1-22 acyl groups are, for example, acetyl, propionyl, butyryl, valeryl, capryl, lauryl, myristyl, palmityl, stearyl, linolyl, behenyl. Examples of a hydroxy-C2-22-acyl group are salicylic acid or lactic acid. Preferred C2-10 carboxyacyl groups are derived, for example, from malonic acid, succinic acid or adipic acid. One example of a preferred C3-10 oligocarboxyacyl group is glyceric acid. A preferred oligocarboxymonohydroxy-C3-10-acyl group is derived, for example, from citric acid or malic acid. Preferred oligocarboxyoligohydroxy-C3-10-acyl groups are derived, for example, from tartaric acid. According to the invention, preferred halogen substituents are fluorine, chlorine, bromine and iodine; chlorine and bromine are particularly preferred. Physiologically compatible salts in the context of the invention are salts of inorganic or organic acids, for example hydrochlorides, sulfates or hydrobromides. According to the invention, the other terms used are derived from the definitions given here.
The ester derivatives of the compounds corresponding to formula (I) also have physiological and hair-structure-improving properties. This applies in particular to the esters of pyridoxine which can be converted by hydrolysis into pyridoxine. In addition, the ester derivatives acquire improved lipid solubility compared with the non-esterified derivatives. Other examples of carboxylic acid ester derivatives of pyridoxine are derived from the carboxylic acids, such as formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, glyceric acid, glyoxylic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, propiolic acid, crotonic acid, isocrotonic acid, elaidic acid, maleic acid, fumaric acid, muconic acid, citraconic acid, mesaconic acid, camphor acid, benzoic acid, o,m,p-phthalic acid, naphthoic acid, toluylic acid, hydratropic acid, atropic acid, cinnamic acid, isonicotinic acid, nicotinic acid, bicarbamic acid, 4,4xe2x80x2-dicyano-6,6xe2x80x2-binicotinic acid, 8-carbamoyloctanoic acid, 1,2,4-pentanetricarboxylic acid, 2-pyrrole carboxylic acid, 1,2,4,6,7-naphthalene pentaacetic acid, malonaldehydic acid, 4-hydroxyphthalamidic acid, 1-pyrazole carboxylic acid, gallic acid or propane tricarboxylic acid, and from dicarboxylic acids selected from the group consisting of compounds corresponding to general formula (II): 
in which Z represents a linear or branched alkyl or alkenyl group containing 4 to 12 carbon atoms, n is a number of 4 to 12 and one of the two groups X and Y represents a COOH group and the other represents hydrogen or a methyl or ethyl group, dicarboxylic acids corresponding to general formula (II) which additionally contain 1 to 3 methyl or ethyl substituents on the cyclohexene ring and dicarboxylic acids which formally are formed from the dicarboxylic acids (II) by addition of one molecule of water onto the double bond in the cyclohexene ring.
The structure-improving effect of the vitamin B6 derivatives on hair keratin can be quantitatively determined by high-pressure differential scanning calorimetric measurements (HP-DSC) of the keratin melting behavior (cf. Examples). The improvement in the fastness of the hair to washing can be quantitatively determined by colormetric measurement of the color difference between colored, unwashed hair and colored, repeatedly washed hair. These effects are particularly noticeable when seriously damaged hair is treated with a composition containing vitamin B6 derivatives. Hair is seriously damaged in particular by oxidizing or reducing treatments, i.e. for example by coloring with oxidation colorants, by bleaching with oxidizing agents or by shaping, for example by permanent waving or smoothing of the hair with strong keratin reducing agents, for example thioglycolate salts or sulfites.
Accordingly, the present invention also relates to a process for the oxidizing or reducing treatment of the hair in which, immediately after the oxidizing or reducing treatment step, the hair is treated with a composition containing a vitamin B6 derivative corresponding to formula I in a quantity of 0.05 to 2% by weight. This aftertreatment composition may be a shampoo, a rinse, a hair-care lotion, a setting lotion, a foam, a hair lotion or a spray, i.e. it may be either a rinse-off product or a leave-on product.
If the composition is applied after coloring of the hair, it may be, for example, a water-based hair-care lotion. If the aftertreatment is to be carried out after the reducing step of a permanent wave treatment, the vitamin B6 derivative may be added to the permanent wave fixing lotion. However, the aftertreatment may also be carried out after the permanent wave fixing step which is of course itself an oxidizing hair treatment. In this case, the vitamin B6 derivative is applied in the form of a hair-care lotion. The composition containing the vitamin B6 derivative is preferably used as a care lotion after oxidative coloring of the hair or for permanent wave fixing. Besides the vitamin B6 derivative, this preparation may contain any of the components which are typically used in the formulation of hair-care preparations and which are compatible with the hair or scalp.
The preparations used for oxidative fixing in permanent waving contain hydrogen peroxide, for example, as oxidizing agent and the stabilizers normally used to stabilize water-containing hydrogen peroxide preparations. The pH value of such aqueous H2O2 preparations which contain about 0.5 to 3% by weight of H2O2 is preferably between 2 and 4 and is adjusted with inorganic acids, preferably with phosphoric acid. However, the preferred oxidizing agent is sodium or potassium bromate. These bromates are used in a concentration of 1 to 10% by weight and the preparations are adjusted to a pH of 4 to 7.
Apart from the oxidizing agents, these permanent wave fixing lotions may contain other components, for example surfactants, quaternary ammonium salts, cationic polymers, water-soluble proteins or protein derivatives, perfumes, opacifiers, etc. A care lotion applied after permanent wave fixing may contain, for example, setting, conditioning, hair-care or antistatic components, alkaline earth metal or aluminium salts and other components.
The process according to the invention is particularly important for structurally improving hair keratin in conjunction with the oxidative coloring and/or bleaching of hair. Accordingly, in a particularly preferred embodiment, the present invention relates to a hair care lotion, more particularly for application after coloring or bleaching of the hair, characterized in that it contains
1 to 10% by weight of emulsified oil, fatty or wax components,
0.1 to 5% by weight of cationic surfactants,
0.2 to 2% by weight of a vitamin B6 derivative corresponding to formula I
in a water-containing carrier.
Suitable oil or fatty components are paraffins, silicone oils, vegetable oils and animal fats (triglycerides), fatty acid fatty alcohol esters (wax esters), fatty acid esters of short-chain alcohols, dicarboxylic acid fatty alcohol esters, linear and branched-chain alcohols and diols containing 10 to 20 carbon atoms, fatty acid monoglycerides and other oils, fats or waxes.
Suitable cationic surfactants are compounds which contain a free or substituted amino group or quaternary ammonium group and, at the nitrogen atom, one or two relatively long-chain alkyl or acylaminoalkyl or acyloxyalkyl groups and up to three short-chain alkyl groups and optionally a benzyl group.
Examples of suitable quaternary ammonium surfactants are
cetyl trimethyl ammonium chloride,
lauryl dimethyl benzyl ammonium bromide,
stearyl trimethyl ammonium chloride,
distearoyloxyethyl dimethyl ammonium methoxysulfate,
cocoacylaminopropyl trimethyl ammonmium chloride.
Other cationic surfactants are, for example, relatively long-chain primary, secondary or tertiary amines in the form of their salts, for example hydrochlorides or sulfates.
In addition to the components mentioned, the hair-care lotions according to the invention may contain, for example, nonionic surfactants and emulsifiers (for the oil and fatty component), water-soluble proteins, protein degradation products or protein derivatives, amino acids (for example serine), water-soluble cationic polymers, setting, film-forming polymers such as, for example, polyvinyl pyrrolidone, glucose and other structuring or scalp-care ingredients such as, for example, panthenol, tocopherol, allantoin, vegetable extracts such as, for example, birch or camomile extract, anti-dandruff agents, vitamins, for example vitamin B1 (thiamine), B2, (riboflavin), B3 (nicotinic acid, nicotinic acid amide), B7 (biotin), B12 (cyanocobalamine), C (ascorbic acid), E (tocopherol acetate), perfumes and UV protection factors.
UV protection factors are particularly important for the long-term protection of hair keratin against the harmful effects of the sun. Accordingly, in a preferred embodiment, the hair-care lotion according to the invention also contains a UV protection factor, preferably in the form of a substance which absorbs ultraviolet rays. Such substances are commercially available in large numbers as either water-soluble or lipid-soluble UV protection factors. In a preferred embodiment, the care lotion according to the invention contains a combination of water-soluble and lipid-soluble UV protection factors.
Suitable water-soluble UV protection factors are, for example,
2-hydroxy-4-methoxybenzophenone-5-sulfonic acid
p-methoxycinnamic acid diethanolamine salt
p-aminobenzoic acid
2-phenylbenzimidazole-5-sulfonic acid
triethanolamine salicylate and
lauryl-[3-(p-dimethylamainobenzamido)-propyl]-dimethyl ammonium-p-toluenesulfonate.
Suitable lipid-soluble UV protection factors are, for example,
2-hydroxy-4-methoxybenzopheneone
2-aminobenzoic acid menthyl ester
4-bis-(2-hydroxypropyl)-aminobenzoic acid ethyl ester
4-aminobenzoic acid-2,3-dihydroxypropyl ester
2-ethylhexyl-2-cyano-3,3-diphenyl acrylate
p-methoxycinnamic acid-2-ethyl hexyl ester
4-methyl benzylidene camphor
4-tert.butyl-4xe2x80x2-methoxydibenzoyl methane.
The care lotion according to the invention is preferably an oil-in-water emulsion of the emulsified oil or fatty components which is either used for washing excess colorant out of the hair or which, after rinsing out of excess dye or excess bleaching agent with water, is applied to the hair in a separate step and uniformly distributed therein.
If the care lotion is to remain on the hair (leave-on product), the content of emulsified oil or fatty components is kept low, preferably below 3% by weight. However, rinsing with cold water is normally carried out after the treatment with the care lotion.
The following Examples are intended to illustrate the invention.